From my perspective, Commander Keen is more of an enemy than The Icon, or specifically the Romero head.

Keen counts towards the kill number and has a proper death code pointer (on frame 774), that also checks for tagged sectors to open as doors. Ok, he doesn't have an attack, but more of that later.

The Romero head does not count for the kill and does not have a proper death code pointer (ie he never goes into non blocking dead body mode). He does scream and create the explosions on his death (frame 780) and then ends the level (frame 783). He does not in fact have an attack either. His "attack" is provided by a separate thing (edit number 89) the spawn cube shooter. Although, I would concede that the Romero head, spawn cube shooter and spawn cube targets could together be considered one entity.

I guess it all depends on your point of view.

"Luke, you're going to find that many of the truths we cling to depend greatly on our point of view."

That's kinda like saying that linedefs, sectors and nodes are all the same thing because they all make a level.

Nah, its more like saying linedefs, sectors and nodes are different parts of a level, which they are. The level is the whole, the lines, sectors and nodes are the parts. The Romero head, shooter and targets are the parts... but I'm not sure where that leaves the lindefs and textures that make up the icon's face.